UNIX 4.2 file system query

[Divyakant Agrawal]

	 UNIX 4.2 allows files to be opened in append mode. I would 
	 like to know if this is "Atomic Append". 

	 For example, if two programs open the same file in append mode,
	 and append few blocks to the file then is it true that the blocks
         will be appended in order (that is first all the blocks of first 
         program followed by the blocks of the second program, or vice-versa).
	 
	 Also, if this is true then is the granularity of atomicity is at
	 block level or is arbitrary. 
	
	 Thanks in advance.

divy